Charge pumps are commonly employed as voltage multipliers to generate the higher voltages needed for the operation of electrically erasable programmable read only memory (EEPROM) integrated circuit (IC) chips. The basic EEPROM circuit operates at a relatively low voltage, such as 3 V or 5 V, but some of the circuit functions require a substantially higher voltage such as an internal 15 volts. This higher voltage is typically provided by means of an on chip voltage multiplier which takes the form of a charge pump.
A charge pump is made up of a plurality of stages driven by a plural phase clock. Typically, the clock is operated at a predetermined frequency and is operated continuously so that the highest available value of boosted voltage is present. A voltage regulator is usually then employed to drop the voltage to the desired level. Since the current required from the boosted voltage is typically low, a shunt regulator can be employed.
This means of generating a high voltage on a chip is wasteful because the excess voltage is reduced by a regulated current drain. The result is an inefficient (in terms of the power consumed) means of multiplying the voltage.
What is desired is a plural phase clock generator which can be used to drive a charge pump in a more efficient manner than presently known clock generators used for that purpose.